Multi-layer Microcapsule Wall for Low Permeability
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Solution Overview
Problem
Conventional controlled release microcapsules face issues such as high permeability in surfactant and water-containing products, limited encapsulation breadth, poor mechanical stability, inadequate surface deposition, and poor environmental biodegradability, leading to premature release and loss of active ingredients, especially in rinse-off applications.
Innovation Solution
A composition of controlled release particles with a core surrounded by multiple layers, including an outer layer of isocyanate and amine reaction products, an intermediate layer of acid and isocyanate reaction products, and an inner layer of acrylate copolymer, which are processed at lower temperatures to achieve reduced permeability and improved adhesion and biodegradability, allowing for controlled release of hydrophobic active ingredients in response to friction and water exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a highly crosslinked membrane is used to reduce permeability and retain encapsulated active, then the barrier performance improves, but environmental biodegradability deteriorates
Solution Approach 1:
The capsule wall is segmented into multiple distinct layers with different functions: an inner layer for mechanical stability, a middle layer for controlled permeability, and an outer layer for biodegradability. This segmentation allows each layer to be optimized independently, resolving the contradiction between overall barrier performance and environmental biodegradability.
Solution Approach 2:
The capsule employs a composite wall structure combining materials with different properties: polyacrylonitrile or polyacrylamide for the inner layer provides stability, while the outer layer uses biodegradable polymers. This composite approach enables the capsule to achieve both low permeability and high biodegradability simultaneously.
2Reliability
If higher reaction temperature is used to achieve higher crosslink density and reduce permeability, then the barrier performance improves, but active ingredient loss through evaporation or thermal degradation increases
Solution Approach 1:
The crosslinking process is segmented into multiple stages occurring at different temperatures. The inner layer is crosslinked first at lower temperatures to preserve heat-sensitive actives, while the outer layer is crosslinked subsequently at higher temperatures to achieve the desired barrier performance without exposing the active ingredient to excessive heat.
Solution Approach 2:
The inner layer is formed and crosslinked preliminarily at lower temperatures before the outer layer is applied and crosslinked at higher temperatures. This preliminary action protects the active ingredient from thermal degradation while still establishing the foundation for achieving low permeability in the final capsule structure.
3Ease of manufacture
If conventional single-layer membrane structure is used, then the manufacturing process is simple, but the capsule prematurely releases active in surfactant and water-containing products
Solution Approach 1:
The capsule wall is segmented into multiple distinct layers with different functions: an inner layer for mechanical stability, a middle layer for controlled permeability, and an outer layer for biodegradability. This segmentation allows each layer to be optimized independently, resolving the contradiction between overall barrier performance and environmental biodegradability.
Solution Approach 2:
The capsule employs a composite wall structure combining materials with different properties: polyacrylonitrile or polyacrylamide for the inner layer provides stability, while the outer layer uses biodegradable polymers. This composite approach enables the capsule to achieve both low permeability and high biodegradability simultaneously.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively retains hydrophobic active ingredients in surfactant-containing solutions, improves adhesion to substrates, and achieves a favorable environmental biodegradability profile, enabling prolonged and efficient release of active ingredients in various consumer products.
Implementation Method 1
Polymers that are used to develop a membrane around the active material need to be crosslinked to provide a sufficient barrier to retain the encapsulated active until its desired release
Implementation Method 2
The permeability and the solubility parameter of this membrane determines the likelihood and the rate of diffusion of the encapsulated active out of the microcapsule
Implementation Method 3
The permeability of such shell material is determined by the crosslink density of the membrane
Implementation Method 4
a shell material is manufactured within the dispersed phase, and migration of the shell material is induced via an interfacial reaction or insolubility of the shell material in the oil phase
Implementation Method 5
Multiple membranes are developed around the core material to reduce the diffusion, and seal the pores
Implementation Method 6
the core is switchable from a low viscosity liquid to a semisolid without using high melting point waxes or polymers
Data Source
AI summary
Disclosed is a composition including controlled release particles, wherein each of the controlled release particles includes: (a) a core including at least one hydrophobic active ingredient; and (b) a wall at least partially surrounding the core and including: (i) an outer layer including a polyurea; (ii) an intermediate layer under the outer layer and including a carbamic-carboxylic anhydride; (iii) an inner layer under the intermediate layer and including an acrylate copolymer; and optionally (iv) an optional outer layer above the outer layer and including a quaternary amine containing moiety, wherein the viscosity of the core can be manipulated from a low viscosity liquid to a semisolid. A method for preparing the composition is also disclosed.